1. Field of the Invention
This invention relates generally to a pulse width modulated signal amplifier (which will be hereinafter referred simply to as a PWM signal amplifier), and is directed more particularly to a PWM signal amplifier which reduces the amplitude distortion in an output voltage.
2. Description of the Prior Art
In the art it is known that since a pair of diodes are connected in parallel to a switching transistor so as to flow a return current from a choke coil of a low pass filter to a current souce, the amplitude of an output voltage from a PWM signal amplifier is different between the time when the diodes are conductive and the time when the switching transistor is conductive and hence the amplitude distortion is caused thereby.
In order to avoid the above defect, there has been proposed the U.S. Pat. No. 3,999,143 entitled in Pulse Width Modulated Signal Amplifier and assigned to the same applicant as that of the present application. In this U.S. Patent, a plurality of diodes other than the return current diodes are used to reduce the amplitude distortion of an output voltage from the PWM signal amplifier.
In this U.S. Patent, however, a relatively expensive diode for high speed operation is necessary as the diode for removing the amplitude distortion, so that the amplifier becomes expensive naturally.